Great game overall, however the bug that was previously mentioned by another user in which the unlocks screen becomes grey also prevents you from actually unlocking anything after it does this. After getting it I assumed it was a fluke, reset the game and played through everything a second time (in an entirely different browser no less) and got the same thing, and once again the medals/features will not unlock.
That said the game concept and design are excellent, I really wish I could give you 5 stars but since this bug seems to consistently render the game completely unplayable (for me at least) in survival mode I will be giving a much lower rating than I would like.
Simply put the half that works is getting 100%... but the other half is a nonfunctional 0%.